Immunoassays employ antibodies as analytical reagents for the detection of analytes. Immunoassays are used to detect the presence of an infectious agent by assaying either for the infectious agent or for antibodies raised by the infected host against the infectious agent. The present invention relates to an immunoassay for detecting antibodies against an infectious agent.
Immunoassays for detecting antibodies can involve two incubation steps. In the first incubation, a sample to be tested is incubated with antigens of an infectious agent which have been immobilized on a surface, for instance the surface of a microwell. Any antibodies in the sample against the infectious agent become bound to the antigens on the surface. After a wash step, the second incubation is performed using antigens of the infectious agent labeled with a detectable substance. Labeled antigen will become bound to the antibodies immobilized on the surface. After a further wash step, the amount of label bound to the surface is determined.
A high signal indicates the presence of antibodies against the infectious agent. FIG. 1 gives a schematic representation of such a prior art immunoassay.
A commercially available example of such a prior art immunoassay is the ORTHO.TM. HIV-1/HIV-2 Ab-capture ELISA test system.
The accurate detection of HIV and other infections is of considerable importance. Early diagnosis of HIV infection enables medical treatment to be started and precautions to be taken in order to limit transmission of the virus. The avoidance of false positives in detecting HIV infection is also of considerable importance.